Clouded Apollos inhabit meadows and woodland clearings with plenty of flowering plants, both in the lowlands and in the mountains.

Northern limits of the clouded Apollo's range appear to be strongly determined by the distribution of its larval host plants (primarily Corydalis solida and the role of climate and relief seem to be of minor importance.

In Carinthia, the environs of Friesach, at an elevation of from 630 to 750 m, there occurs a conspicuously small local form, minor Reb.

In Bavaria and Salzkammergut (Berchtesgaden), at an altitude of about 1000 m (June—July), the species has developed into a constant melanotic form, hartmanni Stgr., the males of which bear an additional grey costal spot in between the apical cell-spot and the widened and dull blackish transparent marginal band, having moreover the abdominal border of the hindwing broader and more densely dusted with black; the females of this form are developed in the same direction as ab.

melaina, but are usually less dark in tint, have a very broad transparent border to the forewing, sometimes a grey S-shaped shadowy transverse band which emanates from the costal spot above mentioned in the male, and possess on the hindwing a more intensely coloured band -like marking behind the cell, extending from the abdominal border forward, and 1 or 2 costal spots.

— athene Stich, is the form inhabiting Greece (Chelmos, Olenos) ; it bears a row of 4 or 5 whitish spots in the moderately broad, posteriorly sharply tapering transparent border of the forewing, otherwise agreeing rather well with ordinary mnemosyne in being somewhat more strongly marked, therefore standing midway between the former and the following form.

(10 f) is the name of the race from Northern Persia and the Caucasus; the white spots in the widened marginal border are more distinctly developed, forming usually a submarginal band consisting of 7 or 8 wedge-shaped or luniform spots; the black markings are intensified and extended, and in the male there appears on the forewing a grey abbreviated band between the apical cell -spot and the transparent border, the forewing bearing further a grey spot at the hind margin and the hindwing bearing an extended dusting of black beyond the cell, forming a kind of band.

An enlarged edition of this form from Central Asia (Kuldja, Alai), with the black markings still more intensified and the transparent border more widened, is known as gigantea Stgr.

Larva cylindrical, tapering at both ends, black, short-hairy, the body ornamented with orange spots; feeds in April and May on Corydalis mnemosyne typ.